matlabimage-processingnoise-reductionimage-enhancement

averaging mask and laplacian mask in image processing


in a given application I apply an averaging mask to input images to reduce noise, and then a Laplacian mask to enhance small details. Anyone knows if I Would get the same results if I reverse the order of these operations in Matlab?


Solution

  • Convolving with a Laplacian kernel is similar to using second derivative information about the intensity changes. Since this derivative is sensitive to noise, we often smooth the image with a Gaussian before applying the Laplacian filter.


    Here's a MATLAB example similar to what @belisarius posted:

    f='http://upload.wikimedia.org/wikipedia/commons/f/f4/Noise_salt_and_pepper.png';
    I = imread(f);
    
    kAvg = fspecial('average',[5 5]);
    kLap = fspecial('laplacian',0.2);
    
    lapMask = @(I) imsubtract(I,imfilter(I,kLap));
    
    subplot(131), imshow(I)
    subplot(132), imshow( imfilter(lapMask(I),kAvg) )
    subplot(133), imshow( lapMask(imfilter(I,kAvg)) )
    

    enter image description here